arm: lpc32xx: switch to common clock framework

The change switches NXP LPC32xx platforms to LPC32xx clock driver
powered by common clock framework, this obsoletes mach-lpc32xx/clock.o
legacy clock driver and thus it is removed.

Legacy timer driver mach-lpc32xx/timer.o strictly depends on legacy
clock support, but fortunately an existing LPC32xx clock source and
clock event driver completely replaces it, and thus it can be removed
as well.

Noticeably platform UART driver directly operates on LPC32xx source
control block registers, remove this dependency to avoid overlapping
with common clock framework driver, also this guarantees that UART is
working expectedly.

Tested-by: Sylvain Lemieux <slemieux@tycoint.com>
Signed-off-by: Vladimir Zapolskiy <vz@mleia.com>